Ancient pollen plucked from the back of a fossilised bee suggests orchids may first have bloomed beneath the feet of the dinosaurs. Tests indicate that the plants first arose between 76m and 84m years ago, meaning they are much older than many scientists previously believed.

The pollen was discovered on the back of a member of a now extinct species of bee - Proplebeia dominicana - that had been preserved in amber in the Dominican Republic. It is among the rarest evidence of pollination in the fossil record.

Scientists have long debated the age of the orchid family, with estimates ranging from their appearance 112m years ago to 26m years ago. Those saying the plants are relatively young point to the near absence of discovered orchid fossils, while others claim their ubiquity around the world and diversity suggests a much older origin.

The orchid family has 20,000 to 30,000 species, making up around 8% of all the world's flowering plants.

Harvard University biologists used the pollen to reconstruct the main evolutionary branches of orchids alive today. Santiago Ramírez, at the University's Museum of Comparative Zoology, said the analysis suggested the family was "fairly young" at the time of the extinction of the dinosaurs some 65m years ago.

Evidence of orchids in the fossil record is rare as the flowers bloom infrequently, and are concentrated in areas where heat and humidity prevent fossilisation.